meson: Refactor libpq targets variables

Some of the knowledge of the libpq targets was spread around between
the top-level meson.build and src/interfaces/libpq*.  This change
organizes it more like other targets by having a libpq_targets
variable that different subdirectories can add to.

Discussion: https://www.postgresql.org/message-id/flat/e8aa97db-872b-4087-b073-f296baae948d%40eisentraut.org

meson.build

@@ -3121,6 +3121,7 @@ add_project_link_arguments(ldflags, language: ['c', 'cpp'])
 # list of targets for various alias targets
 backend_targets = []
 bin_targets = []
+libpq_targets = []
 pl_targets = []
 contrib_targets = []
 testprep_targets = []
@@ -3547,20 +3548,13 @@ endif
 installed_targets = [
   backend_targets,
   bin_targets,
-  libpq_st,
+  libpq_targets,
   pl_targets,
   contrib_targets,
   nls_mo_targets,
   ecpg_targets,
 ]
 
-if oauth_flow_supported
-  installed_targets += [
-    libpq_oauth_so,
-    libpq_oauth_st,
-  ]
-endif
-
 # all targets that require building code
 all_built = [
   installed_targets,
@@ -3897,7 +3891,7 @@ add_test_setup('running',
 ###############################################################
 
 alias_target('backend', backend_targets)
-alias_target('bin', bin_targets + [libpq_st])
+alias_target('bin', bin_targets + libpq_targets)
 alias_target('pl', pl_targets)
 alias_target('contrib', contrib_targets)
 alias_target('testprep', testprep_targets)

src/interfaces/libpq-oauth/meson.build

@@ -32,6 +32,7 @@ libpq_oauth_st = static_library('libpq-oauth',
   ],
   kwargs: default_lib_args,
 )
+libpq_targets += libpq_oauth_st
 
 # This is an internal module; we don't want an SONAME and therefore do not set
 # SO_MAJOR_VERSION.
@@ -47,6 +48,7 @@ libpq_oauth_so = shared_module(libpq_oauth_name,
   link_args: export_fmt.format(export_file.full_path()),
   kwargs: default_lib_args,
 )
+libpq_targets += libpq_oauth_so
 
 libpq_oauth_test_deps = []
 

src/interfaces/libpq/meson.build

@@ -65,6 +65,7 @@ libpq_st = static_library('libpq',
   dependencies: [frontend_stlib_code, libpq_deps],
   kwargs: default_lib_args,
 )
+libpq_targets += libpq_st
 
 libpq_so = shared_library('libpq',
   libpq_sources + libpq_so_sources,
@@ -79,6 +80,7 @@ libpq_so = shared_library('libpq',
   link_args: export_fmt.format(export_file.full_path()),
   kwargs: default_lib_args,
 )
+libpq_targets += libpq_so
 
 libpq = declare_dependency(
   link_with: [libpq_so],